In a back-illumination type CMOS image sensor (CIS), part of incident light, especially light in a long wavelength band is not sufficiently absorbed and passes through a photoelectric conversion unit formed of a photodiode and the like, and enters a wiring layer. Then, transmitted light is reflected by a wire of the wiring layer and enters a photoelectric conversion unit of an adjacent pixel, thereby causing color mixture and deteriorating image quality.
Therefore, in the related art, proposed is a technology in which a reflection layer made of tungsten is formed on an opposite surface of a light incident side of a substrate layer formed with a photoelectric conversion unit. Since the light having passed through the photoelectric conversion unit is reflected in a direction to the same photoelectric conversion unit by this reflection layer, occurrence of color mixture is prevented (refer to Patent Document 1, for example).